1. Field of the Invention
The invention relates to a method of reconditioning a rotating turbine blade following the use in a high temperature environment or as part of the production of a new blade and in particular to the reconditioning of the blade shroud.
2. Brief Description of the Related Art
Blade shrouds for gas turbines as disclosed in US 2001/0006600 are typically used to reduce primary leakages by providing a seal between the rotating blade and a stationary component, for example a honeycomb or abradable system fastened to the turbine inner casing. A typical shroud element includes a shroud platform and one or more knife-edges extending radially away from the platform with respect to the turbine rotor and towards the stationary component on the turbine casing. These knife-edges can be placed along the edges of the platform as well as on a center portion of the platform. A shroud cavity is defined by the knife-edges define together with the platform and the stationary component opposite the blade shroud.
A blade shroud constitutes an additional mass at the extreme radial distance from the blade root, which cause increased centrifugal forces and resulting stresses in the root region of the blade.
During operation of the turbine blade the shroud can be damaged by creep deformation or lifting of the shroud, mainly of the shroud platform. Such deformations of the shroud can lead to mismatches between adjacent blade shrouds and hot gas ingestion into to the shroud cavity with resulting over heating of the shroud.
Blade shrouds damaged in this way have until today been considered as irreparable. Therefore, they have been traditionally replaced by a blade with a complete new design aimed at an increased blade lifetime, which may include the design of cooling channels within the shroud in connection with a reduction of the weight of the shroud as suggested for example in US 2001/0006600.
DE 199 25 781 discloses a method for reshaping a turbine component by fixing the component to a matrix having a specified mould, immersing the component into an incompressible medium such as water or oil, and introducing a pressure wave into the medium. However, in this method the design of the blade and the driving force of the blade degradation is not changed and no increase in blade lifetime can result.